* Delta (0–4 Hz). You're basically unconscious—either sleeping or, God forbid, comatose.
* Theta (4–8 Hz). The semiconscious realm between sleeping and waking—you're dozing, but not fully asleep. During theta activity, you access stored images of peak performance (like dunking over your buddy during a pickup hoops game).
* Alpha (8–13 Hz). Your "idle" brain state. At the low end, you're daydreaming; at the high end, in a state of relaxed alertness. The optimum range for most conscious activity is between 8/9 Hz and 15/16Hz.
* Beta (13–21 Hz). Your state of greatest alertness. The lower end of the range corresponds to linear thinking and problem solving. At the high end of the range, however, you've really redlined your anxiety, and your body may tense up and become difficult to control.